Radiotransmitter



Dec. 15 1925. 1565505 F. M. RYAN RADIO TRANSMITTER Filed Aug. 14, 1924 4 Sheets-Sheet 1 'IIII SYSTEM Z0 L. E PANEL lnren/ar: franc/k M. )Tyan RADIO TRANSMITTER Filed Aug. 14, 1924 4 Sheets-Sheet 2 I II f H 74 6 .75

l l v H. F. PANEL lnven/or: Francis M. Ryan y Ah] Dec. 15, 1925' 7 1,565,505

F. M. RYAN RADIO TRANSMITTER Filed-Aug. 14, 1924 4 Sheets-Sheet 4 l I I 1 V7 Va 3/ H72 RA. PANEL "Wen/0r:

Francis/7. lfyan.

by My Patented Dec. 15, 1925.

UNITED STATES PATENT orrice.

FRANCIS M. RYAN, or EAST ORANGE, NEW JERSEY, AssIGNoa T0 WESTERN ELEC- TRIO COMPANY, I CORPORATED, or NEW YORK, N. Y., A CORPORATION or NEW YORK.

RADIOTRANSMITTER.

Application filed August 14, 1924. Serial No. 731,906.

To all whom it may concern:

Be it known that I, FRANCIS M. RYAN, a citizen of the United States of America, re-

siding at East Orange, in the county'of Essex and State of New Jersey, have inventedcertain new and useful Improve ments in Radiotransmitters, of which the following is a full, clear, concise, and exact description. I

The present invention. relates to wave transmission systems and particularly to radio transmission systems.

The invention has particular application in radio transmitting, systems involving a considerable amount of high frequency en ergy. In such systems it is advantageous to use vacuumtube amplifiers to increase the radio frequency power to the level required. Where a number of such amplifiers are used it becomes a highly important matter not only to supply the operating voltages to the tubes in eflicient and convenient manner but to develop control systems, which will permit the necessary circuit changes to. be

' made without injury to the apparatus or to the operators and without requiring the expenditure of unnecessary time or waste of energy. These controls may be for starting the system into operation or stopping it or changing its adjustment. In any case, it is desirable to accomplish the controlling action quickly, safely, and expeditiously.

An object of the invention is to effect the necessary controls of a vacuum tube system in a simple and efficient manner.

A related object is to supply the operating voltages to vacuum tube circuits and similar apparatus in an efiicient manner.

Features of the invention comprise:

A polyphase power distributing circuit for supplying the anode circuits of space discharge tubes.

An automatically operating starting circuit for causing the successive units of a tube system to start in predetermined seustment of a radio transmitter to another wave length adjustment.

Arrangements for securing the most efiicient power output adjustments at the various settings of the system.

Lock-out arrangements for the control system to insure safety of operation.

Restart features whereby after a shift in the circuit adjustments, the system is caused immediately and automatically to take up. efiicient operation on the basis of the new ad ustment; and various features concerned in the operation and control of the system, as will appear more fully hereinafter.

In" a system involving potentials of only a few hundred volts and an output of only a few hundred watts, it is a comparatively simple matter to supply the necessary operating voltages and to make changes inthe circuit manually without danger to the operator, and in any sequence without injury to the apparatus. In the system to be described more fully hereinafter, however, embodying the present invention, the radio frequency power developed in the antenna may amount to many kilowatts, requiring that potentials of several thousand volts be supplied to the tube circuits. Special problems arise in such a system of supplying the power to the tubes and obtaining economical operation of the various parts of the circuit and of protecting operator and apparatus from injury on account of the large voltages. As stated above, there is the further problem of effecting changes in adjustment of the system as may be found necessary.

' The various provisions of the invention for side by side with Fig. l to the left, show in schematic form the circuit arrangements of a complete radio transmitter. according to the invention.

For convenience in the description the apparatus on the drawing has been divided into four panels. The portion of the system shown on Fig. 1 is designated the low frequency panel, that on Fig. 2 the high frequency panel, that on Fig. 3 the power panel and that of Fig. 4 the power amplier panel. It is to be understood, of course, that in actual practice the apparatus may be distributed in this or in an other manner upon any desired number 0 panels, or otherwise disposed.

General signal transmission circuit.

station A or SS at station B. A telegraph key 3 at station A and a similar one at station B are also supplied for controlling the radio station in accordance with telegraph messages, in a'manner to be described hereinafter.

The telephone apparatus is connected by the aid of suitable switching devices to be described later to the primary of the repeating coil 5, the secondary of which feeds into the voice amplifying circ'uit VA of Fig. 1.

. This amplifier comprises in the specific circuit illustrated two stages of amplification, the first comprising a three-element vacuum tube 6 of usual construction and the second stage comprising the two tubes 7 and 8 1n parallel. The amplified output of the amplifier VA is supplied to the late circuits of the modulator M, which is s own as comprising a pair of three-element vacuum tubes 28 and 29 connected in parallel. The grids of the tubes 28 and 29 are supplied by an oscillator 0 comprising a three-element vacuum tube 27 provided with the pro er "circuits for causing it to generate radio 'requency oscillations. Modulation of these radio frequency oscillations by the amplified speech is effected in the modulator tube 011- cuit M, and the resulting modulated waves are su plied to the grid circuits of the power ampli er PA. The amplified modulated waves from the power amplifier PA are supplied through suitable coupling circuits to the transmitting antenna TA.

It may be noted at this point that four manners of indicating conductors have been -,adopted for convenience in reading the "drawing; the light-weight solid line 1s re- .served for the relay and control conductors and Signal" transmission conductors not ineludingftubes; the light-weight broken *is'fu'sed to indicate filament heating circuits;

the heavy line is used to indicate plate current supply circuits; and the heavy broken line is used to indicate grid biasing circuits.

The various circuits for energizing tubes will be pointed out more in detail hereinafter. It-will suffice to point out here that space current is supplied to the second stage of the voice amplifier VA and to the modulator M in parallel through the high inductance 30 as is indicated by the heavy solid line. Between the voice amplifier and the modulator a small inductance 33 is included in the plate supply lead to serve as a high frequency choke coil to prevent the transfer of radio frequency oscillations fromthe modulator M to the voice amplifier VA or choke coil 30. This method of modulation is more fully described in the United States patents, to R. A. Heising 1,442,146 and 1,442,147, dated January 16, 1923. Radio frequency choke coils are indicated in the cathode plate leads of tubes 7, 8, 28 and 29 and in the common plate lead of the power amplifier tubes for preventing the production of undesired sustained oscillations.

The oscillator 0 comprises, as stated, the

tube 27 and the tuned circuit generally indicated at 34. This comprises an inductance 35 to the opposite terminals of which the grid and anode, respectively, of tube 27 are ada ted to be connected, and variable capacities 36 and 37 connected in series across inductance 35 with the filament of tube 27 connected between the capacities. By moving the handle WL the amount of capacity and inductance connected between the various terminals of the tube 27 can be varied at will to alter the frequency of the oscillations generated. Further reference to this feature will be made hereinafter.

Bridged across the radio frequency output circuit of the modulator M is an antiresonant circuit 38 comprising capacity 39 and inductance 43 connected in parallel between the lead 42 and ground. The purpose of this anti-resonant circuit is to improve the transmission characteristics of the circuit as will be indicated more fully hereinafter.

Actuation of the handle WL to change the frequency of the oscillator also changes the tuning of circuit 38.

The antenna circuit comprises the loading inductance 44 connected adjustably to a parallel circuit having one branch composed of the tuning inductance 45 and the capacity 46 in series to ground and the other branch comprising the capacity 47. The radio frequency output circuit from the power amplifier passes through the blocking condenser 48 to a. variable tap on tuning inductance '45. The. path to ground from the power amplifier PA thus includes an adjustable amount of inductance 45 and capacity 46 and by varying the adjustments provided for inductance and condensers 46 and 47' by means of the wave length handwheel VVL the antenna tuning may be changed and any suitable coupling may be obtained, as will be explained more in detail hereinafter, the switches WL v and VL, are mechanically connected so as to move together so as to insure that the oscillator tuning,-the' coupling, and the. antenna tuningall have the proper relation for satisfactory operation.

. Power supply.

The power supply for energizing all of the vacuum tube circuits is derived primarily from the three-phase generator 20, Fig. 1. This eneiator supplies power directly to the primary 40, from the secondary 50 of which are derived the anode potentials for the power amplifier PA.

The operating voltages for all of the vacuum tubes on the low frequency panel and on the high frequency panel are supplied from motor generator sets indicated in 1 ig. 2 supplied with power from generator 20. These comprise the motors 51 and 52 and the generators driven thereby, of

which 53 supplies'filament heating current for the tubes on these two panels, 54 supplies plate potential, while 55 supplies grid polarizing potential for both of these panels and also for-the power amplifier.

The primary 40 of the power transformer is shown delta connected, although it might have been some other suitable type-of connection, while the secondary 50 is shown as distributedY connected. This is also called an interconnected star arrangement.

Thus the primary winding shown in the drawing in the. vertical position would have as its secondary windings the two half coils of secondary 50 that are in the vertical position, these three windings being placed on the same core.

their respective secondaries, the half coils of secondary 50 that are shown parallel with the primaries. In this wayeach limb of the transformer core carries, in addition-to a primary w1nd1ng, two secondaries, one from each of two phases.

Each secondary circuit or phase. is connected to one of the rectifiers, so that only direct current flows in the secondary wind-- ings. By connecting the coils in this manner the direct current in one of the two secondary windings on one transformer leg just ncutralizes that in the other winding so that there is no direct current flux from the rectified .current in any of the trans:

former legs. This fact means that less iron need beg-used 1n the core than if. the secondaries werenot distributed and that the. efficiency is raised on account of the reduction of the core losses.

In a similar manner, the other primary windings would have for power amplifier. Condenserz59' is bridged across the amplifier plate sup 1y leads and forms a low impedance path or these harmonics and also for speech frequency components present in the power amplifier plate current.

Individual gaps are shown connected between each secondary terminal and ground. and also from the neutral to ground for safety purposes with series resistance to limitthe current.

, Radio frequency inductance 49, inserted between the direct current ground and the antenna ground, is not essential but is convenient in case a counterpoise is to be used in place of the antenna ground. In such case if the alternating current branch of the "paver amplifier were connected directly to the filament ground, a considerable portion of the antenna current would be shunted around the counterpoise capacity. Choke 4:9 prevents this but readily passes the smaller tube-output alternating current.

The cathodes of the power amplifier and of the rectifier tubes 56, 57 and 58 are heated by alternating current obtained by transformers from the three phase power supply leads 61, 62 and 63. The primary windings of the filament heating transformers are connected across the leads 1n rotation to distribute the load equally among the phases.

St art control.

It has been pointed out above that both.

the alternating current and the direct cur-- rent voltages developed in a radio trans- Jnitter of the form being described amount to, many thousand volts in a transmitter of considerable power output. In a form of transmitter used'by the inventor, the power I amplifiertubes and also the rectifier .tubes were of the type in which the anodes are cooled bycirculating water. In order to prevent injury "to the tubes, it is essential that the power be shut off from the tubes immediately in case of failure in the cooling system, or 1n case of an overload due to a short circuit or a wrong adjustment of the circuit. It is also important to apply the v potentials to the tube elements in the proper sequence. It has been found advantageous from the standpoint of safety to the tubes to establish a relatively large negative grid potential in the power amplifier before the anode potential is applied to the tubes. This procedure is also important to a lesser extent in the tubes employing less power. It is desirable also, in the case of the voice amplifier and modulator tubes, to apply the tube potentials in steps in order to prevent too large a voltage surge from taking place through the choke coil 30.

The automatic start control for insuring the proper application of the operating voltages to the various tubes as outlined above, will now be described. A group of relays is provided on the low frequency panel cooperating with a second group of relays on the high frequency panel for enabling the starting operations to take place in sequence from a sin 'le control button. This obviates the necessity of the attendant watching meters or alarm devices and exercising a succession of controls, and by simplifying the .control procedure makes the system adapted for starting and stopping from an outlying station.

The start control circuit is arranged for actuation from the start control button in conjunction with certain safety circuits repairs, etc. When this switch 64 isclosed,

the leads 17 and 18 are energized from-the generator 20 and these leads supply operating voltage for the various relay circuits.

The lead 31 for energizing switching relay 13 passes through contacts on the wave length controls WL and VVL and also through certain relay contacts to be described hereinafter, so that relay 13 is deenergized and power from the generator 20 is cut off from the supply leads 61, 62 and 63 unless all of the series. contacts in lead 31 are closed. Similarly, the lead 32 which supplies locking current-for the relay 14 contains a number of overload contacts in series, so that in case extraordinary voltages are produced at certain critical points in the system, lead 32 is opened, causing relay 14, to deenergize and open the circuit of switching relay 13 and certain relays on the high frequency panel cutting oflz' the power supply from the entire set. Similar provision is made for shutting 01f the power under control of door switches which are indicated diagrammatically in Figure l, and from water pressure and temperature indicators as will be described later on.

With this brief description of the general arrangement of the starting circuit, the specific arrangements can best be described from tracing through the operation of starting the system. 1

Assuming that the doors through which I entrance to the rear of the apparatus is gained are all closed, and, that the attend- -telegraph transmitting key and the subscribers set at station A or' the correspond- .ing apparatus at station B to the control circuit and radio transmitting system. Depending therefore on whether the station selecting switch is in its lower or its upper position as shown in the drawing, closure of switch 1 or switch 4 energizes relay- 9 througha circuit including grounded battery 2, relay 9, upper or lower contacts of switch SSW and switch 1 or switch 4 to ground. Relay 9 in energizing, closes the circuit for relay 10, from battery 2. Relay .10 applies voltage from source 20 across the leads 17 and 18, causing the immediate energization of relay 11. Relay 11 applies power from the source 20 to the motors 51 and 52, causing them to start up the various generators. 53, 54 and 55 for supplying filament, anode and grid polarizing to the tubes as described hereinbe ore. The field of the filament current generator 53 is normally closed through resistances 66, 67 and 68, this machine being self-exciting. After it is set into motion therefore, voltage is.'developed across the filament heating leads '71 and 72, causing after a time, the energization of the marginal relay 12 which is slow to energize. Generator 55 also develops its full load voltage across the grid polorizing leads-73 and 74, causing the application of grid polarizin potential to all of the tubes throughout are system. A smoothing condenser, 97, is shown connected across these leads. Since the field circuit of generator 54 is open at this time, at the right hand front contact of relay 24, no anode voltage is applied to the tubes on the low frequency and high frequency panels.

One or the other of the motors 51 or 52 is assumed to drive a suitable pump for circulating water through the cooling system for the power amplifier and rectifier tubes. For the sake of simplicity in the drawing,

no attenipthas been made to show the pump or any of the circulatory system for the tubes except that in Fig. 1, the water pressure indicator 75 is shown. After the water circulation reaches its normalgate, contacts otentials,

of the pressure indicator 75 become opened, thus removing the shunt which previously existed across the winding of relay and this relay is now energized from loads 17 and 18. Relay 1:) closes at its front contact a circuit in parallel with its own circuit for relay 19 through leads 17 and 18. Relay 19 is slow to energize and before it has time to break its right hand back contact, a circuit for relay 14 is closed from lead 17, through one of the door switch contacts, winding of relay 14, resistance 76, right hand back contact and armature of relay 19 to lead 18. It will be noted that relay 14 was shunted through the back contact of relay 15 up to-the time that relay 15 became energized. Relay 19 closes a locking circuit for itself through its left hand armature and front contact. Relay 14 closes a locking circuit for itself through its left hand armature and front contact and lead 32, provided the overload relays 77', 78 and 41 are not energized. With the arrangement of relays thus far described, it will be clear that, except for the auxiliary start and stop buttons 121 and 122, to be described presently, if relay 14 has its locking circuit broken at any point, it will 'not be reenergized by a reestablishment of= this locking circuit but it can be energized only by first energizing relay 15, with relay 19 deenergized. This situation can-only exist by purposely disabling the system as by opening leads 17 and 18. v

'VVhile it would suflice, so .far as the operation of the starting circuit is. concerned, to have only the circuit elements that have been described, it is eonvenient to provide an auxiliary start button 121 and a stop button 122. These may be mounted at any placeon the set within easy reach of the attendant. 'lhese buttons when depressed make momen tary contact and enable relay 14 to be energized or deenergized at will, independently of the condition of relays 15 and 19. -For example, if relay 19 is energized so that the system could not be restarted from either start key 1 or 4, key 121 may be depressed to close a circuit from conductor 18, normal contacts of relays 41, 78, 77 and conductor 32, resistance 76, winding of relay l4, door switch. contact, to conductor 17, thus starting the system in the manner described. Closure of key 122 shunts relay 14 causing it to deenergize and shut the power off from the power panel and power amplifier in the manner already described.

Relay 14 being energized and locked as de scribed, a circuit is closed through relay 13 from lead 17, winding of relay 13, right hand armature and front contact of relay 14, conductor 79, contact of relay 25 (this relay having been energized when the grid polarizing generator was started) conductor 31, contact on the power control handle PC, contact on the wave length switch VVL ,'to

conductor 18. Relay 13 in energizing con-' nects the power leads 61, 62 and 63 to gener ator '20 and current is thus applied to the filament heating transformers of the power amplifier PA and the rectifier tubes 56, 57 and 58 causing'thc filaments of these tubes to light, and also to the primary winding 40 of the power transfm'mer through contacts of one of relays 84, 85, 86 as will be more fully described hereinafter.

\Vhcn current was applied to the leads 17 and 18 by the energization of relay 10, relay 21 became energized over a circuit extending fronrlead 17, winding of relay 2]., conductor :31. contacts on the power control and wave length controls as above traced to conductor 18. Relay 21, like relay 19, is slow to energize, and before its armature breaks contact,

relay 22 is energized from conductor 17, contact on the door switch, winding of relay 22, armature and contact of relay 21, lead 31 to conductor 18 as previously traced. Relay 22 at its right hand contacts extends the plate current supply leads from generator 54 to the voice amplifier oscillator and modulator tubes and at its left hand contact closes a circuit for relay 23 extending from conductor 17, contact of the door-switch, left hand armature of relay 22, winding ofrelay 22- contact of relay 26, lead "31 to conductor 18 as previously traced. Re-

lay 26 is an overload relay and under normal conditions remains unoperated. Relay 23 in energizing closes a circuit at its left hand armature for maintaining relay 22 energized, thiscontact being inparallel with the contact-of relay 21 so long as relay 26 is deenergized. So long therefore. as there is no break in conductor 31 and no abnormal plate current to cause relay 26 to energir'te, (the door switch being assumed to remain closed), relays 22 and 23 remain locked up. Should either relay become deenergizcd, except for the auxiliary control buttons 123 and 124, it is impossible for it to reenergize without first deenergizing relay 21 which can only occur through a break in conductors 17 and 18. or in lead 31. I

Button 123 is an auxiliary starting button similar to 121, and when depressed enables relay 22 to be operated to start the high frequency panel supply system regardless of the energized condition of relay 2].. Also button 124 when depressed, momentarily opens the locking circuit for relays 22 and suddenly.

PC, switch segment for telephony TP, con ductor 83, winding of relay 81 to conductor '18. Relay 81 in energizing at its right hand contact closes a short circuit around resistance 66. At its left hand contact relay 81 connects the filaments of the voice amplifier tubes across the leads 71 and 72- causing the filaments of these tubes to become heated.

Resistance 66 is a compensating resistance to keep the filament voltage constant for the two load conditions corresponding to telephony and telegraphy. As will be indicated hereinafter, the tubes 6, 7 and 8 are out of circuit when the set is used for. telegraph, the filament circuit for these tubes being opened at the left armature of relay 81, so that less load is placed on the filament heating generator than when telephoning. Whenever relay 81 is energized, therefore, to include the filaments of tubes 6, 7 and 8 in circuit, the resistance 66 is shunted to increase the field excitation of generator 53 to keep its output voltage the same.

Upon the energization of relay 23, a circuit is closed for relay 24, from conductor 17 through attendants switch 65, front contacts of marginal relay 12 (this relay having been energized when the filament generator 53 started) winding of relay 24, right hand contact of relay 23, contact of relay 26, lead 31 to conductor 18 as previously traced. Relay 24 in energizing establishes the field circuit for the plate current generator 54 through its right hand armature and contact across leads 71 and 721 At the same time relay 24, at itsleft hand contactbridges the resistance 67, in the field circuit of generator 53. Generator 54 gets its field excitation from generator 53, so that when relay"? 24 cuts in the generator 54 it is necessary to increase the field excitation of generator 53 to keep its output voltage the same with the increased load on it. This is done by shunt ing resistance 67 as described. The plate current for the tubes on the low frequency paneland high frequency panel is caused in this manner to build up gradually since time is required after the closure of the field circuit of generator 54 to develop its full voltage, so that no sudden application'of space current is made through chokefcoil 30 and any resultant harmful effects from a high voltage discharge from this coil are thus avoided. Since relay 22 must always energize before relay 24, the armature circuit of generator 54 is closed before the field,

and this arrangement further prevents the production of transients in the plate supply circuit due to charging the capacities When current was applied tothe conductors 17 and 18, a circuit was closed through .one of the three power control relays 84, 85, 86, this circuit extending from conductor 17, lead 82, switch arm 104 of power control switch PC, one of the right hand contacts of this switch arm and the corresponding relay 84, 85 or 86 to lead 87 and conductor 18. The particular relay 84, 85 or 86 to become energized depends upon the setting of the power control switch PC. This will be described more fully hereinafter. Whichever of these three relays energizes will connect through 1118 three individual armatures, selected points on the primary winding 40 of the power transformer to the three phase power supply leads 61, 62 and 63 causing the power transformer 40, 50 to become energized to supply space current through the rectifier tubes 56, 57 and 58, to the anodes of the power amplifier PA. From the foregoing description, it will be seen that as a result of closing either switch 1 at the radio station A or switch 4 at the outlying station B, the entire radio transmitting circuit has become energized and except for wave length and power control adjustments which may be necessary is in condition for the transmission of signals.

From the description which has already been given of the signal transmission circuit, a very brief description'will sulfice to make it clear how the various portions of the circuit operate in the transmission of speech. Assuming that the wave length and power control adjustments have been made for the of any desired type of. radio receiver indicated at R or R, for receiving a return messa from the distant station with which radiocommunication is to be had. The radio receiver R, or R will, of course, be

providedxwith connection to an antenna which may be of the well known loop type or any suitable type and which will preferably be oriented or positioned to receive from the distant; radio station, but to be free of undue interferences from the local radio station.

The speech currents from the repeating coil 89 pass through the contacts of station selecting switch SSW to the primary of repeating coil 5 by which they are impressed on the grid of the amplifier tube 6. The amplified speech waves from the tube 6 are impressed on the second stage. amplifiers 7 and 8 and in the manner that has already been described are caused to modulate the radio frequency wave supplied to the moduof the holes in the flange 93 to lockthe lated waves are then amplified in the power iv-( 06 lea I571, change.

The system illustrated in the drawing is adapted for both radio telephone transmission and radio telegraph transmissiom'upon any one of a number of difierent wave lengths. As has already been indicated, the wave length of the set is changed by means of the wave length switches \VL, and WL, In an actual embodiment of the apparatus, the switches \VL and L, are connected mechanically either by suitable gearing, sprocket wheels and chains, or cables so that a single control Wheel such as VVL serves to change the antenna tuning, the oscillator tuning and the'tuning of the anti-resonant shunt circuit 38. For sake of-simplicity of the drawing such mechanical interconnec tion has not been illustrated. The switch Vii, is shown as comprising a hand wheel 91, mounted in suitable bearings (not shown) on the framework 92. The wheel 91 carriesa flange 93 with a number of holes at different points along it, corresponding to the various wave length positions. A pin 94, projects from the framework 92 in such position as to extend through one or another wheel 91 against rotation. Then it is desired to change to a new wave length, the wheel 91 is first pulled outward (downward in the drawing) to disengage the pin 94 from the flange 93. The wheel 91 is splined on the shaft 95, so that the wheel may 'be' pulled lengthwise of the shaft without moving the shaft lengthwise. After thus releasing wheel 91, it-may be turned to any desired wave length position and then pushed. inward (upward in the drawing) to cause the pin 94 to lock the wheel in the new position. It is impossible to move the wave length switch L without first unlocking it in this manner.

. Whenever the wheel .91 is withdrawn to enable it to be rotated, contact springs 96 are separated and lead 31 is opened. This lead, it will be recalled, supplies current from conductor 17 through the winding of relay 21 and also through. the windings of relays 1 -1, 22 and 23 to the return conductor 18, so that when lead. 31 is broken, all of these relays deenergize. Relay 13 in deenergizing, opens the power supply leads 61, 62 and 63, thus cutting ofi all power from the power panel and from the p wer amplifier and rectifier tubes. Relay 22 in deenergizing opens the plate circuits of the voice amplifier, oscillator and modulator tubes. Relay 24 is also deenergized when relay 23 deenergizes, and relay 24 is preferably made to operate more quick 1y than relay 22 so that the filament'currents energized contacts, etc.

of the tubes on the low frequency and high frequency panels is reduced and the field circuit of the plate generator 54 is opened before relay 22 breaks the plate circuit loads. In this manner excessive voltages are prevented from being generated through choke coil 30.

The power being automatically shut off from all of the tubes of the set when the handle of the wave length switch WVL is withdrawn, this switch may be moved to any new position without the necessity of breaking any high voltage circuits, shunting As soon as the readjustment has been made and the handle of the wave length switch has returned to normal as described, conductor 31 is reestablished and relays 13 and 21 immediately energize, relay 13 applying power again to the power panel and power amplifier panel and relay 21 as explained in the description of the starting operation, causing relays 22, 2:) and. 24 to energize and reestablish the power connections to the anodes of the tubes on the low frequency and high frequency panels.

The anti-resonant circuit 38 is as explained above tuned to the radio-frequency and thus offers a substantially infinite impedance to waves of the radio-frequency across the radio-frequency output branch of the modulator M. Since the impedance offered by this circuit rapidly decreases for Power change- T6lephmw-telegraph control.

As indicated hereinbefore, the system shown. in the drawing is adapted both for radio-telephone and radio-telegraph transmission. In the form illustrated, different; amounts of radio-frequency power are used for the two kinds of. transmission, and, of course, the voice frequency amplifier VA is not required for telegraph transmission. According to the invention, a unitary power control switch PC is provided for shifting quickly from one type of transmission to the other and for effecting the necessary changes in the tube circuits to accommodate the two kinds of transmission. It is found inpractice that different power or different impedance adjustments are desirable for different wave lengths and a further provision is made on the-power control switch for altering the power and impedance relays of the circuit as maybe desired.

The power control switch PC is provided with a hand wheel 101 substantially like that of the wave length switch 'VVL and also has the mechanical lock features described in connection with the wheel "VVL lV hen a change is to be made in the adjustment of the power control switch PC, the hand wheel 10! is first withdrawn to enable the wheel to be rotated, and in such withdrawal the lead 31 is broken at contacts 102. This causes relays 13, 21, 22, 23 and 24 all to become deenergized as above described and to disconnect the power sources from all of the tube circuits. As soon as the hand wheel 101 is restored to position to close contacts 102, theserelays again execute the cycle of operations above described to reapply power to the tubes of the system. The central arm 104 of the power control switch moves over two segments TP corresponding to radio-telephone transmission and TG corresponding to radio-telegraph transmission. As has already been described when the switch is set for telephone transmission, relay 81 is energized, causing the filaments of the voice amplifier tubes VA to be lighted. When the adjustment is changed to that for telegraph transmission, the central switch arm 104 is moved off from the segment TP on to the segment TG, thus opening the circuit of relay 81 and removing the filaments of the voice amplifier tubes from circuit. A ,circuit ,is now established through relay 103 this circuit extending from conductor 17,-1ead 82 (Fig. 3) switch arm 104, segment-ITP, winding of relay 103, lead 105 to conductor 18. Re-

' lay 103 energizing, closes 'a short-circuit around choke coil 30 and at its right-hand contact, opens the 'normally closed circuit extending from a point between the grid circuit resistances 106 and 107, to ground. The full potential generated across the grid resistance 106 is thus applied to the tubes 27, 28 and 29. This resistance 106 is so proportioned with respect to resistance 107 that when the shunt is opened around it, the negative grid voltage rises to such a high value as to substantially reduce the space current of tubes 27, 28 and 29 to zero. In an actual system used by applicant, the voltage of generator 55 together with the other constants of the circuit were such that when the shunt around resistance 106 was opened, the negative grid voltage rose to about 300 volts, while with the shunt circuit established around resistance 106, the negative grid voltage was much less, being merely that developed in the grid leak. A second shunt circuit 108 in parallel with that through the right-hand contact of relay 103 leads to contacts of the telegraph relay 109 (Fig. 1) and is-adapted to' be opened and closed by the armature of relay 109 whenever the telegraph key 3 at station A or the corresponding key at station B is closed.- In this manner the grid potential of the tubes 27 2S and 29 is varied under control of the telegraph key 3 to cause the space current to be alternately large and substantially zero to produce telegraph controlled radio-frequency wares. These radio-frequency waves are amplified by the power amplifier PA and impressed on the transmitting antenna.

The amplitude of the radio-frequency waves impressed on the power amplifier from the modulator M is controlled by taps along the resistance 111, these taps being connected to thepower amplifier input by the switch arm 112, under control of the switch PC. The polarizing potential of the grids of the power amplifier, is controlled by switch arm 113, which establishes connection from the grids through the radio-frequency choke 114 and conductor 115 to switch arm 113 and to taps along resistance 116', bridged across the grid polarizing potential leads 73 and 74.

The power adjustment for the power amplifier is made under control of switch arm 104 and its cooperating contacts for controlling relays 84, 85, and 86. Depending upon the setting of the switch arm 104, one or another of these three relays is energized to include one or another number of turns of the primary coils 40 in circuit across the power leads 61, 62 and 63, thus varying the step-up voltage ratio of the transformer.

Safety circa/5t.

If the pressure gauge 75 (Fig. 1) in re-v sponse to a decrease in the flow of water closes its contacts, a short-circuitis established across relay 15, causing this relay to deenergize. In case the temperature of the water becomes too high, relay 16 is energized to close a similar short-circuit across relay 15. In either case, relay 15 deenergizes and at its back contact closes a shortcircuit across relay 14 extending from upper door switch contact, winding of relay 14, back contact of relay 15, and then to the upper contact of the door switch again. Relay 14 deenergizes, opening at its rlghthand contact, conductor 79 and causing relays 13, 21, 22, 23 and 24 to deenergize. As in the cases described above, relay 13 disconnects the relay generator 20 from the i the system is disabled as a. result of any one power and power amplifier panels and relay 22 opens the plate supply circuit of the voice amplifier VA and the oscillator and modulator tubes.

In case of an overload in the power amplificr, resulting in an abnormal increase in space current, through the power amplifier or rectifier tubes, relay 41 (Fig. 4) energizes and opens conductor 32. This conductor would also be opened if either overload relay 77 or 78 on the power panel becameenergized, due to an abnormal current being drawn by the power transformer. In

- either case, the effect of opening lead 32 is to break the normal locking circuit of relay 14, causing this relay to deenergize and open conductor 79, at its right-hand contact. Relays 13, 21, 22, 23 and 24 then become deenergized as described above, causing the poiver to be shut down on all of the panels.

t is

lay 14 to become deenergized, relay 19- remains energized, due to the locking circuit extending through its left-hand armature. Except for the attendants auxiliary controls 121 and 122, it is therefore impossible to reenergize relay 14, without first opening conductors 17 and 18. This arrangement is desirable in that the attention of the operator is necessary to restart the system when it is automatically shut down by an abnormal and dangerous condition. For example, in the case of a partial obstruction which did not sufiiciently reduce the pressure of the cooling system, to operate the contacts of the gauge 75, .the temperature might rise sufficiently to energize relay 16 and cause the power to be shut down. With the type of control provided by the invention as described above, it is made impossible for'the system to restart in case it merely stands idle until the temperature drops sufliciently to open the circuit of relay 16 again.

The circuit of relay 14 as'described, also includes a contact of the door switch. It is therefore impossible to start the system or to-appl'y any high voltages thereto, until the door by which rear of the panels are closed, or in case a door is opened while the system is operating and an attendant goes to the rear of the panels, the system will not restar-t by the accidental closing of the door.

means of the dual control, a restart y takes place immediately after either a wave Y length or a power readjustment of the cir-' cuit, whereas a restart can only be made by the deliberate act of an attendant in case of a number of abnormal conditions.

What is claimed is: 1. In combination, a plurality of space discharge tubes, circuits for supplying to be noted that in either of the abnormal conditions above noted, causrng readmission is gained to the power to said tubes, circuit controllers therefor, a start key, and means actuated in response to the closure of said start key for successively operating said controllers to close physically the supply circuits to said tubes in a predetermined timed sequence. I

2. In combination, a space discharge device having a cathode adapted to be heated, and an anode, a cathode heating circuit, a space current su ply circuit, a generator having a field an an armature for energizing said space current circuit, circuit closing devices for said circuits, means for closing the field of the space current generator dependent upon the circuit closing device for the space current circuit having been reviously actuated, said means being also ependent for its operation upon the cathode-heatingcircuit having been previously energized. r

3. In a vacuum tube system, space dischargeelectrodes comprising a cathode to be heated and an anode, energizing circuits therefor, a start key, and automatically operating means for first energizing the cathode in response to the actuation of said key. and for thereafter gradually energizing the anode circuit.

4. In combination, a s ace discharge device having a cathode an an'anode, a generator having afield amd an armature for supplying space current to said device, switching means for closing the, armature circuit only when the field energization is substantially zero, and switching means op erating in response to the actuation of said first mentioned switching means for energizing the field.

5. Ina radio transmitter, an oscillation generator having a resonant circuit for detel-mining the frequency of the oscillations generated, an antenna circuit, .connections between said generator and said antenna, an anti-resonan circuit in. bridge of said connections, and means for simultaneously changing the constants of the tunedv circuit of said generator, said anti-resonant circuit and said antenna in tune with the generator, and the bridged circuit anti-resonant at the wave length being transmitted.

6. In a radio transmitting system, space discharge tubes, energizing circuits therefor, ad usting switches for said system, a circuit for initially closing said energizing circuits in predetermined sequence, means actuated in the operation of the system-adjusting switches for opening said circuit to deenergize said tubes, and means actuated from the system-adjusting switches for again ener izing said'tubes upon the establishment o a new adjustment. i

7. In a radio transmitting system, a space discharge tube, energizing circuits therefor,

to maintain the antenna g discharge tube,

a system-adjusting switch, a control gircuit adapted when closed tocause the energization of the tube circuitsi in redetermined sequence and when open to I eenergize the tube circuits, and means .controlled in the initial movement of the adjustin switch for opening said control circuit'an controlled in the final movement of said adjusting switch for closing said control switch.

,8 In a radio transmitting system, a space a series of control devices for-said energizingcircuits, a control circuit for automatically actuating said control devices in predetermined seque nce, andv a safety circuit actuated in response to abnormal conditions.

of said system arranged to actuate said control circuit. 1

' 9. In a radio transmitting system, a space discharge tube, energizing circuits therefor control devices for opening and closing sai circuits, a manual control, a control circuit for automatically operating said devices to energize said tube circuits in predetermined: sequence and. to deenergize said tube circuits, said control circuit being a controlled in said manual control, and a safety circuit actuated in response to an abnormaL'condition of said system, including means for causing said control circuit to .deenergize said tube circuits and for rendering said safety circuit powerless to cause reenergiza- I tion of the tube circults. O

10. In combination, having cathode, I electrodes, energizing circuits. for- 5 space discharge tube anode.and grid or control heating the cathode and supplying space current're-,

recti spectively, a circuit for, biasing the grid negative-with respect tothe filament, and

means for establishing current flow inY the cathode heating andspace current circuitsonly u on the previousapplication to the; grid 0 -a'negative potential.

1,1. In a radio transmitter, a spacedis charge tube, a source of three-phase "alters nating current for supplying space' discharge current thereto, a space' 'discharlge e er foreach phase "for rectifying t ener iz' circuits therefor g y different secondary cirbn the secondary side including. in clrcuit with a said rectifier two' se'con ry coils on different core branches.

.1 13. In aradio transmitting system, a plurality of vacuum tubes, energizing circuits.

therefor, wave-change switchesfor the system, means for initially. energizing said .tubes,

and means for deenergizing said tubes in response to.1mt1at1ng the movement of one-of said wave-change switches and for re-- energizin said tubes in res onseto the completion-o movement of sa1 switch;

14. In a radio transmitting system employing a plurality of vacuum tubes, means or making automatically shutting off the power supply to-said tubes while a change in the circuit is thetwo secondary. the respectivecore legs a space.

changes in the circuit, means for" being made and for switching the power on I to. the tubes when the circuit change has been made.

15. In a radio traiismitting system, means to transmit radio waves modified in accord ance with telegraph and with. telephone signals alternatively, a switchfor altering the circuits from. one kind of signaling to the other," and means controlled from said Switch for changing the power. output of said system.

lnyfitness whereof; Ihereunto subscribe y a 1924, I I FRANCIS M. RYAN.

me this 12 day of" August A. D., 

